Modular fuel element adaptable to different nuclear power plants with cooling channels

Abstract

The present invention relates to a modular nuclear fuel element, which can be adapted by an assembly system allowing it to be used in different nuclear power plants with horizontal and vertical cooling channels. The odule is a cluster of parallel fuel rods mounted as circular concentric crowns and supported by a structural system. It has a single diameter fuel rod array where the ratio of the heat transfer surface defined per unit length to the ransverse rod cross section is higher than 330. It also has selfsupporting fuel element spacer grids, which are collapsible sheaths attached to them with fewer than 13 welded end stoppers. The number of these fuel rods is higher than 43. The length of the module is the largest compatible length with the refuelling machine, to reduce the hydraulic restrictions caused by structural endings, and to be able to balance this by providing a fuel element having a larger cooling area. This will maintain the hydraulic restriction and the current total fuel mass in the channel. The modular fuel element may contain fuel material combinations with different uranium and/or plutonium isotopic concentrations, and/or any other nuclear fuel material (actinides, nuclear poisons, fission products or fuel material coming from other nuclear reactors). The utilisation of the fuel modules individually in the pressurised heavy water reactors with horizontal fuel channels is an application of the present invention. Another application would involve the assembling of several fuel modules in nuclear reactors with vertical fuel channels.